Invitro immune responses in children following BCG vaccination

Abstract

Introduction: There is still no consensus on the efficacy of BCG vaccine in the prevention of tuberculosis. This study therefore addressed the question of the magnitude of immunity afforded by BCG, by studying the effector mechanisms of protection in children. The main objectives were to assess the degree of immunity conferred by BCG vaccine in children and to identify the most immunogenic antigen(s) of BCG by conducting in-vitro studies. Materials and methods: Children in the age-group of 1 to 10 years, were categorized: (A) normal, and vaccinated with BCG during the first year, n=45, (B) normal, without scar and with no evident history of vaccination, n=31: and (C) children admitted in the hospital with a confirmed diagnosis of tuberculosis, n=31. Fractions of BCG were obtained by lysis, sonication, separation by gel chromatography, HPLC and confirmed by SDS-PAGE. In lymphoproliferative assays PBMC were cultured and stimulated with either Concanavalin-A or Tuberculin or the fractions of BCG. Stimulation indices (SI) in lymphoproliferation, CD4/CD8 cells, levels of Interferon-γ (IFN- γ) in the culture supernatants were measured by ELISA. Results: The vaccinated children displayed significantly high (P< 0.05) mean values of SI in LTT, CD4/CD8 cell ratio against the unfractionated, 67kDa fraction and BCG-CF Ags. While 100% of the vaccinated children had positive lymphoproliferation indices to BCG-CF, only 8.3% of the unvaccinated children were positive. Conclusion: Some of the components of BCG induced a strong Thl cell response in children. These immunogenic antigens were present in the whole cell lysate. The use of BCG vaccine for tuberculosis is worthwhile till a new vaccine is developed.

Keywords

• BCG vaccine
• Children
• Immune responses
• T cells
• IFN- &#947;